Have you filed in probate court and received an appointment as executor form the court? Until you do this you have no legal standing. Once you have done this it is your responsibility to take possession of all the assets of the estate and to pay all of the bills from those assets. Anything left over is to be distributed in accordance with the will or state law. The clerk at the probate court can provide you with information that will answer most of your questions.
Family members should not be allowed to remove anything until the estate is settled. Call a locksmith and have the locks changed.